PvPIndex MCBans

Added

• Multi-module Maven build: pvpindex-mcbans-api (JitPack-publishable HTTP client) and pvpindex-mcbans-plugin (Paper plugin fat JAR).
• jitpack.yml - JitPack CI support for pvpindex-mcbans-api.
• MySQL / MariaDB and PostgreSQL storage backends via HikariCP.
• rban command for banning offline (never-joined) players.
• PlaceholderAPI expansion.

Changed

• Project rewritten from scratch under the PvPIndex platform; original MCBans API replaced with PvPIndex REST API.
• Storage layer refactored: SQLite remains the default; MySQL and PostgreSQL added as optional backends.
• Permission backend now configurable: SuperPerms (default), Vault, or OPs.
• Background sync uses a delta endpoint (/bans/sync) instead of full re-download.
• Failsafe mode is now opt-in (failsafe: false default) rather than enabled by default.

Fixed

• String reference-equality comparisons (==) in MCBansAPI replaced with isEmpty().
• Duplicate @param in MCBansAPI.tempBan javadoc.

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